An anastomosis is a surgical procedure by which two separate tubular bodies or ducts, usually blood vessels, are interconnected. The anastomotic connection allows body fluid to flow between the lumens of the tubular bodies without leakage at the connection site. Such a connection may be required to repair severed blood vessels. More often, anastomotic connections are utilized in order to bypass an obstruction in a patient's heart. For example, in a coronary artery bypass graft (CABG) surgery, a graft vessel is anastomosed to the coronary artery downstream from the obstruction to enable aortic blood carried by the graft vessel to be rerouted around the blockage in the coronary artery. In one case, the anastomosis may be made between the end of the graft vessel and the side wall of the coronary artery, in what is typically known as an end-to-side connection. In other instances, the anastomotic connection could be of the side-to-side type. And in certain situations, more than one anastomotic connection may be needed.
Current methods available for creating an anastomotic connection include hand suturing the vessels together. However, the use of sutures to connect interrupted vessels has inherent drawbacks. For example, suturing is difficult to perform and time-consuming, and requires great skill and experience on the part of the surgeon due in large part to the extremely small scale of the vessels. Suturing is particularly difficult in beating heart CABG surgery. Also, sutures do not always provide a fluid-tight connection at the anastomosis site. Moreover, to perform the procedure it is usually necessary to stop the heart by infusing the organ with cold cardioplegia solution. This enables a blood-free and still anastomosis site for the suturing process. However, such procedures for slowing down or stopping the heart inherently result in trauma to the organ.
Attempts have been made to provide implantable devices that connect blood vessels together in a more expedient and reliable manner. One approach is to use staples to create an anastomotic connection. For example, Kaster et al. in U.S. Pat. No. 5,234,447 describes a staple comprising a rigid metal ring having fingers radially extending therefrom. Using a staple forming tool, the fingers are deformed to urge them into engagement with the vessels' interior and exterior walls, thereby creating an anastomotic connection between the vessels.
One potential problem arising with staples having rigid annular members is compliance mismatch. The use of flexible metallic anastomotic staples for CABG procedures has recently been proposed to address this problem. Some of these flexible staples are described by Gifford, III et al. in U.S. Pat. Nos. 5,695,504 and 5,817,113, Backinski et al. in U.S. Pat. No. 6,036,702, and by Derowe et al. in WO 99/62408. These staples have flexible annular means that may reduce the rigidity of solid annular members of other staples such as the one described by Kaster et al.
In addition, use of flexible metallic stents has been contemplated to address the problem of compliance mismatch. Nevertheless, stents may eventually suffer from physiological phenomena such as intimal hyperplasia and stenosis. Gifford, III et al. in U.S. Pat. No. 5,695,504 attempts to overcome the problem of intimal hyperplasia by providing a non-absorbable flexible filament as a base to hold vessel engaging members. However, the non-absorbable flexible filament may not have the rigidity needed to deploy the staple, and may further radially constrain the vessel. Finally, the nonabsorbable filament may sterically hinder secondary interventional techniques such as balloon angioplasty that may become necessary at a future time.
Current designs for vascular anastomotic staples generally are more successful in large diameter proximal anastomoses. However, their utility in smaller diameter proximal anastomoses and distal anastomoses may be limited. Most of the anastomotic staples described in the art have rigid or substantially rigid annular members that serve as the base for vessel engaging members. These annular members may induce neointimal hyperplasia through a mechanism similar to that observed with metallic stents. Another potential problem with these annular members is that they may preclude the possibility of interventional means to address the hyperplasia, such as balloon angioplasty. Finally, rigid or semi-rigid metallic annular members may complicate the use of secondary interventional devices such as balloon or stent-carrying catheters by sterically preventing or hindering access to lesions distal to the staple.
There is thus a need for a vascular anastomosis staple that provides fast and reliable anastomosis in small diameter vessels. There is also a need for an anastomosis staple that prevents incurrence of neointimal hyperplasia. Finally, there is also a need for an anastomosis device that does not sterically hinder access to the surrounding tissue by other devices such as catheters.